1. Field of the Invention
The present invention relates to a method and a system for mounting electric components on a printed-wiring board to produce printed circuit boards.
2. Related Art Statement
There are various manners of mounting electric components (“ECs”) on a printed-wiring board. For example, Japanese Patent Document TOKU-KAI-HEI No. 6(1994)-196546 discloses an EC mounting system which includes a movable member which is movable to an arbitrary position on a horizontal plane; a main moving device which moves the movable member; a rotatable body which is attached to the movable member such that the rotatable body is rotatable about a vertical axis line; and a plurality of suction nozzles which are supported by the rotatable body such that the suction nozzles are provided along a circle whose center is located on the axis line of the rotatable body and such that each of the suction nozzles is not rotatable relative to the rotatable body and is movable relative to the body in a direction parallel to the axis line of the body. In the EC mounting system, owing to combination of the movement of the movable member and the rotation of the rotatable body, the suction nozzles sequentially stick and hold respective ECs, and sequentially mount the ECs on respective EC-mount locations on a printed-wiring board.
The above EC mounting system further includes an image taking device which is fixed in position. When the suction nozzles all holding the respective ECs pass by the image taking device, the image taking device take respective images of the ECs held by the suction nozzles, and the mounting system calculates, based on image data representing the taken images, position errors of the EC held by each of the suction nozzles. The position errors include respective position errors of the center of the EC in two directions perpendicular to each other on a horizontal plane, and a rotation-position error of the EC about a vertical axis line of the each suction nozzle. The position errors of the center of the EC are corrected by correcting respective distances of movement of the movable member in the two directions, and the rotation-position error is corrected by rotating the rotatable body. Thus, the EC is mounted with a correct rotation position at a correct EC-mount location on the printed-wiring board.
However, the above EC mounting system employs a plurality of engaging members corresponding to the plurality of suction nozzles, respectively, and revolves the engaging members with the corresponding suction nozzles, so that whichever rotation phase each of the suction nozzles may take, the corresponding engaging member can engage the each suction nozzle, thereby move the nozzle toward the printed-wiring board supported by a board supporting device, and mount the EC on the board. Thus, a great mass is moved with the movable member and accordingly it is difficult to start and/or stop the movable member so quickly, which leads to limiting the improvement of EC mounting efficiency.
The above problem that a great movement mass limits the improvement of EC mounting efficiency is encountered by not only the EC mounting system disclosed by the above-indicated Japanese Patent Document but also an EC mounting system of a type (hereinafter, referred to as the rotatable-body-moving-type EC mounting system) which includes a rotatable body and a plurality of suction nozzles supported by the rotatable body, and which moves the rotatable body along a plane perpendicular to an axis line of rotation of the body and thereby mounts ECs held by the suction nozzles on a printed-wiring board.
Moreover, there is an EC mounting system of a type which includes a rotatable body and a plurality of suction nozzles supported by the rotatable body, and which does not move the rotatable body but moves a printed-wiring board to mount ECs held by the suction nozzles on the board. In this EC mounting system, if a plurality of engaging members are employed and provided on the rotatable body, for moving the corresponding suction nozzles toward the printed-wiring board supported by a board supporting device, the rotatable body is subjected to an increased moment of inertia. Thus, it is difficult to start and/or stop the rotatable body so quickly, which leads to limiting the improvement of EC mounting efficiency.